Method for writing and reading data by fluorescence on a light-sensitive substrate, and related substrate and devices

Abstract

A method for 3D recording of data on a medium formed from a transparent photosensitive material including at least one dopant. The method includes a first step of calibrating and checking a pulsed light source including calibrating the number of pulses, the level of fluence of each pulse emitted and the rate of the pulses and a step of inscribing an area of the material. The fluence of each pulse emitted, the number of pulses and the rate of the pulses are suitable for irradiating the material in the area so as to form fluorescent clusters stabilized from the dopant while minimizing the modification of the refractive index and the absorption coefficient of the medium in a wavelength range from visible to near infrared.

The invention claimed is: 
     
       1. Method for 3D recording of data on a medium formed from a transparent photosensitive material including at least one dopant, said method including:
 a first step of calibrating and checking a first pulsed light source including calibrating the number of pulses, the level of fluence of each pulse emitted and the rate of the pulses; and 
 a step of inscribing an area of the material, 
 
       wherein the fluence of each pulse emitted, the number of pulses and the rate of the pulses are suitable for irradiating the material in said area such as to form fluorescent clusters stabilized from the dopant, each cluster forming a fluorescent emitter, the spectrum and the intensity of fluorescence of which correspond to a signature for encoding a data word, said stabilized clusters being obtained while minimizing the modification of the refractive index and the absorption coefficient of the medium in a wavelength range from visible to near infrared. 
     
     
       2. The data recording method according to  claim 1 , wherein the first source of light is calibrated such that:
 the rate of the pulses is greater than a second predetermined threshold for creating a temperature that is greater than a third temperature predetermined threshold in the irradiated area; and 
 the duration of each emitted light pulse is shorter than the characteristic time of thermalization of the material such as to excite the area of the medium by multiphoton ionization. 
 
     
     
       3. The data recording method according to  claim 1 , wherein:
 the rate of each pulse of the first light source is greater than 1 kHz; 
 the fluence of each pulse transmitted is substantially close to 1 J·cm −2 ; and 
 the wavelength of the laser is at least two times greater than the cut-off wavelength of the transparent medium. 
 
     
     
       4. The data recording method according to  claim 1 , wherein the first light source includes at least one of the two following light sources: an infrared femtosecond laser, and an infrared picosecond laser. 
     
     
       5. The data recording method according to  claim 1 , wherein the medium is formed from a glassy material and the dopant includes at least one type of metal ion of the set of following ions: silver ion, gold ion, and copper ion. 
     
     
       6. The data recording method according to  claim 1 , wherein the irradiation step comprises a set of pulses on a same area of the medium so as to form stable irradiated clusters, the formed clusters defining a fluorescent emitter, the spectrum and the intensity of fluorescence of which, corresponding to a given calibration of the first light source, defines a signature. 
     
     
       7. The data recording method according to  claim 1 , wherein the rate of the pulses of the first light source is substantially equal to 10 MHz. 
     
     
       8. The data recording method according to  claim 1 , wherein the steps of the recording method are repeated on a set of areas located at a same depth of the medium, the set of the areas located at a same depth being called a layer, each calibration of the first source being suitable for an inscription given on each of the areas, wherein the method can be repeated on superposed layers of the medium.